In military applications, two types of towed vehicles are well-known and often used for weapons/gunnery practice and aircraft protection. These vehicles are aerial towed targets and aerial towed decoys, respectively. Aerial towed targets are typically towed behind an aircraft and used in conjunction with pilot training exercises. Aerial towed decoys are used to draw various types of guided weapons away from an aircraft that the weapons are intended to destroy and/or used to evaluate the effectiveness of guided weapon systems. An example of an aerial target is shown in U.S. Pat. No. 4205,848 to Smith et al., with examples of aerial decoys being shown in U.S. Pat. Nos. 4,718,320 to Brum and 4,852,455 to Brum, the disclosures of which are incorporated herein by reference.
Aerial towed targets and decoys which include electronic devices and circuitry incorporated therein have been known in the prior art for many years. In particular, aerial targets often include various electronic devices which are used for purposes of scoring the pilot's performance during a training exercise. Electronic decoys contain various types of electronic circuits to create an apparent target to a weapon to attract the weapon to the decoy, rather than the aircraft. One such active electronic device is a transponder which is adapted to receive radar signals and rebroadcast an amplified return signal. In addition to electronic decoys, various types of thermal decoys are known in the prior art which include flares designed to attract infrared guided missiles. The flare or transponder of the decoy is designed to present a larger thermal or electronic target than the aircraft from which it is deployed and thereby attract the weapon away from the aircraft. As the programming of anti-aircraft weaponry becomes more sophisticated to better discriminate between decoys and aircraft, the need to provide decoys with enhanced capabilities similarly evolves. Moreover, insofar as different anti-aircraft weapons utilize different types of electronic or thermal imaging systems, there exists a need to maintain an adequate inventory of decoys to defeat an attack by any of a variety of different types of anti-aircraft weapons that may be fired at the aircraft.
Though some types of aerial targets are intended to be recoverable, the majority are intended to be non-recoverable or sacrificial. As will be recognized, decoys by their very nature are intended to be exclusively sacrificial since the tow line is typically cut at the aircraft at the end of a flight or mission, or immediately upon the destruction of the decoy. One of the most critical stages in the utilization of both recoverable and sacrificial towed vehicles is in the initial deployment thereof. In the event a towed vehicle, and especially a decoy, is destroyed by a missile or other weapon, it is desirable to deploy a second decoy as rapidly as possible. The difficulty regarding deployment lies in the fact that the tow line must be able to withstand the extreme amount of tensile force exerted thereon by the drag of the vehicle during the deployment operation, particularly at the end of the payout of the vehicle.
In one currently known deployment technique, the tow line is wrapped or folded at either the aircraft end or the towed vehicle end, and allowed to pay out freely without braking. This particular deployment technique is primarily utilized in conjunction with sacrificial towed vehicles. In using this particular technique, the elasticity of the tow line must absorb the kinetic energy arising from the relative velocity of the towed vehicle to the aircraft at the end of the towed vehicle payout. As can be appreciated, oftentimes the tow line will snap during the deployment, rendering the target or decoy irretrievably lost. Additionally, this particular deployment technique is only effective at relatively low aircraft speeds since at higher aircraft speeds, the mass of the tow line itself prevents full use of its elasticity which typically results in line failure at the end of the payout.
In view of the deficiencies associated with the aforementioned deployment technique, a second more popular technique of rapidly deploying both sacrificial and recoverable towed vehicles involves the fixing of spools at either the aircraft or the towed vehicle to control the payout and braking of the tow line. The tow line is wrapped about the spool and allowed to be payed out in a controlled manner via the application of a mechanical braking force to the spool. In certain prior art systems of this type, rapid deployment of the towed vehicle is facilitated by utilizing a centrifugally applied brake in conjunction with a spool having a large outer-to-inner tow line diameter ratio. In the centrifugally applied brake, springs are typically used to hold off brake elements in a centrifugal clutch until a desired rotational speed of the spool for brake engagement is achieved. In other types of centrifugally applied brakes, shear pins or detents are used to hold off the brake elements. Once a desired rotational speed of the spool is achieved, the pins shear, thus facilitating brake engagement.
A principal limitation in the use of various types of thermal and electronic decoys is the space limitation relative to the inclusion of useful quantities of decoys on an aircraft. In this respect, it is often desirable to dispose a decoy deployment system within the aircraft space used for an existing flare, chaff or other expendable decoy round. Packaging the required tow line length into the narrow spaces which are usually available in the aircraft typically necessitates the use of tow line spools which are longer (sometimes several times) than their diameter. When the tow line is pulled from the spool through a guide disposed intermediate the spool flanges, it forms a pull-off angle with respect to the remainder of the tow line wrapped about the spool. As the spool length increases in relation to its diameter, the maximum pull-off angle also increases. Since the tow line is under high tension loads when a towed vehicle is deployed at high air speeds, the combination of the small bend radius of the tow line and the line-to-line abrasion caused by the high pull-off angle often results in tow line breakage at only a fraction of its rated load. As such, it is highly desirable to reduce the tow line pull-off angle to minimize occurrences of tow line breakage. Though the pull-off angle may be reduced by moving the guide radially outward away from the spool, the same spacial limitations that necessitate the use of an elongate, narrow spool preclude such a design modification.
The present invention addresses the aforementioned need in the prior art by providing a deployment apparatus wherein the tow line is routed from the spool over one or more bars located peripherally around the spool. Such routing effectively increases the distance from the point where the tow line leaves the spool to the guide, thereby reducing the pull-off angle, while not significantly increasing the size or packaging volume of the deployment apparatus. The bars may be rotatably mounted on bearings, or may be stationary and include a low-friction coating applied thereto.